SABCS: Breast Cancer Vaccine Seen Promising

Action Points

Explain to interested patients that researchers are studying vaccines against several cancers, both as therapeutics and as preventives, but that few have been validated in clinical trials.

This study was published as an abstract and presented orally at a conference. These data and conclusions should be considered to be preliminary as they have not yet been reviewed and published in a peer-reviewed publication.

SAN ANTONIO, Dec. 15 -- An investigational breast cancer vaccine consistently reduced the rate of disease recurrence by about 50%, according to combined results of two small non-randomized studies, researchers reported here.

The vaccine, based on the HER2/neu protein, shows sufficient promise that researchers are seeking approval for a phase III randomized trial, said Col. George Peoples, M.D., of Brooke Army Medical Center in Fort Sam Houston, Tex.

The finding was "very exciting to us," Dr. Peoples told a plenary session of the San Antonio Breast Cancer Symposium, but he added that because of the small numbers the difference lost statistical significance in the most recent analysis.

The researchers enrolled 186 women with completely treated breast cancer, who were disease-free when they entered the trial and had an intact immune system, Dr. Peoples said. Both node-positive and node-negative women were enrolled.

The vaccine was a peptide dubbed E75, derived from the HER2/neu protein and combined with granulocyte macrophage colony simulating factor (GM-CSF) and was injected intradermally, Dr. Peoples said.

The peptide binds to the HLA A2 molecule, found in about half the population, and stimulates CD8 killer cells, he said. Women in the studies served as controls -- and were not vaccinated -- if they did not have the HLA A2 molecule.

After a median 20 months of follow-up, Dr. Peoples said:

Overall survival was 99% among vaccinated women and 95% among controls.

Disease-free survival was 92.5% for those who were vaccinated and 77% among controls.

The recurrence rate was 5.7% among the vaccinated women and 14.1% among the controls, which was statistically significant at P<0.04.

However, a late recurrence in the active arm changed the overall recurrence rates after 24 months of follow-up to 8.3% for the vaccination arm and 16% for the controls, which was no longer statistically significant, he said.

"This is a small trial and more importantly has a low event incidence, which means that even a single patient can change the results," he said.

He noted that the findings are based on a "mixed bag of patients" who -- because the research began as a dose-finding study -- got varying doses of the vaccine. A randomized controlled trial has been designed, he said, and the researchers are asking the FDA to evaluate it under a Special Protocol Assessment.

"These are highly preliminary data that suggest that further research should be done," commented Eric Winer, M.D., of the Dana-Farber Cancer Center in Boston. But he cautioned it's "way too early" to suggest that the vaccine is effective.

"This was two combined data sets, non-randomized, small numbers, (with) short follow-up," Dr. Winer said, but "it's interesting and certainly enough to lead to additional research."

Dr. Winer moderated the session in which Dr. Peoples presented his data and was not involved in the research.

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